Observing Evolution

Observing Evolution January 17, 2012

Creationists regularly claim that evolution is unobservable. This claim is false. To give some examples, just in recent days there have been a few important instances of scientists being able to witness crucial evolutionary transitions as they happen. Here are links to relevant articles:

In yeast, scientists have observed the transition from being a single-celled organism to multicellularity.

In a particular type of skink (a lizard), we have been able to witness the transition from laying eggs to live births.

The instance of an organism which straddles the distinction between plant and animal illustrates not only that the categories we use of “species,” “phyla” and even “kinds” are artificial and do not reflect the actual world, but also helps us understand how an animal or plant might transition from one category to the other in the course of its evolution. I wonder how a young-earth creationist would argue that an organism of this sort fits the claim in Genesis that each thing is made according to its “kind.”


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  • Kirt Onthank

    I like your post, but the last link is painful.   First off, Mesodinium chamaeleon is not an “animal” at all, ciliates are protozoans (Chromalveolates), and actually more closely related to plants than to animals.  Then then take up algae and live symbiotically with this algae.  Interestingly, the Cryptomonad algae that the ciliates are taking up are in the same group of protozoans they are (also Chromalveolates) 
    This is type of symbiosis is not new, and is done more impressively by other animals (check out Elysia chlorotica).  It also does not make the resulting pair of organisms a “hybrid”, they are still distinct organisms. 
    So when io9 asks “is Mesodinium chamaeleon a plant or animal” an answer that it is both, they are sorely mistaken.  It is neither, and isn’t even particularly  good example of an organism that rides the fence.

    • Thanks for the clarification on the last point! Please do share some specific better examples of organisms that straddle the fence or are in the process of transitioning in some way, if they come to mind!

  • Kirt Onthank

    My favorite example is mentioned above: Elysia chlorotica, a sea slug (or nudibranch) that consumes marine algae.  Now unlike the protozoans mentioned in the above article, E. chlorotica actually digests the algae, but keeps its chloroplasts, which it places in its tissues to continue the photosynthesis.  Now this is where it gets really interesting:  Normally a chloroplast can’t survive very long outside the algal cell it came from, there are genes in the alga’s nuclear genome that need to make making products for the chloroplast to survive. Most symbioses like their solve this one of two ways: keep the whole algae alive in your cells to keep doing its work (like sea anemones do), or simply keep consuming more algae to harvest chloroplasts from as the previous ones die.  In contrast E. chlorotica appears to have “stolen” several genes the chloroplast needs to survive from the alga they feed on: Vaucheria litorea.  Because of this these sea slugs can now keep these chloroplasts alive for very long periods of time. 
    Anyhow, that is what I think is the best examples of blurring the lines between plant and animal, but the sea slug is still an animal, and wouldn’t be confused for a plant by any competent biologist.  Although things are getting a bit muddier due to horizontal gene transfer and other phenomenon, the process of evolution has created a very real pattern in the life.  There is a very real division between, say, primates and cows, or plants and fungi, based on there seperate descent.  While we recognize and name these descended clusters of animals, it isn’t really true that “the categories we use of “species,” “phyla” and even “kinds” are artificial and do not reflect the actual world”.  When a biologist speaks of a phylum, or genus, or family, we are speaking of a group of animals that all share a common ancestor that is not shared by other groups of animals:  that is a reflection of the real world. 

  • domy

    What differentiates the DNA of the single yeast from the ‘multicellular yeast’?

    • I presume (someone correct me if I am wrong) that it is too soon to expect the genome of the multicellular yeast to have been sequenced, compared with the yeast from which it evolved, and the results published. But given how important the step of shifting from single-celled to multicellular organism is, I am sure that this research will be done, and done soon. I’d keep my eye on the science magazines and/or journals – or blogs, which sometimes break the news first these days.